1. Field of the Invention
The invention relates in general to push button electrical switch assemblies, and more specifically to electrically and mechanically reliable push button and electrical switch assemblies which include contact wiping engagement of their contact elements.
2. Description of the Prior Art
Certain applications for push buttons are more severe than others, such as those used as elevator car call buttons in an elevator car, and elevator hall call buttons in the hallways of a building. These push buttons are subjected to constant usage by the public, and thus they must be built to withstand intense service. They are also subjected to considerable abuse, both intentional and unintentional. Thus, they must be constructed such that they do not invite vandalism, such as by eliminating visible fastening devices. Further, they must be constructed such that they will withstand abuse and vandalism, such as being able to withstand actuation by an umbrella point, and extreme closing pressures, without external or internal damage.
Elevator push buttons have still additional requirements which set them apart from the average push button use. They must notify the user that a call has been entered by illuminating a predetermined portion of the push button after actuation, and the illumination must be maintaned until the call is answered.
In addition to reducing the number of service calls by constructing the push buttons to withstand high usage, abuse and vandalism, they should be constructed to be easily and quickly serviced, when service is necessary. For example, the light source in the push button, or any other elements thereof, must be easily and quickly replaceable by authorized personnel without the necessity of using special tools.
In addition to being mechanically reliable, elevator push buttons must be electrically reliable. Elevator systems are currently being constructed with low voltage, solid-state devices. Thus, the elevator push button should be able to make good electrical contact between its contact elements, when used with low DC logic level voltages and currents, and of course it should be equally suitable and adequately electrically insulated for use with higher AC and DC voltages.
While the above requirements place stringent demands on the structure and design of elevator push button electric switch assemblies, these requirements must be met with an assembly which is economically attractive, i.e., it must be easily manufactured of low cost components, and it must be susceptible to quick and accurate assembly without requiring special skills or exacting labor.